The present invention relates to signal systems for transmitting signals within aircraft.
Many types of signal are required within an aircraft, during normal operation. For instance, control signals are required for instructing appropriate operation of plant of many kinds. Responses to control signals may be required, to allow for monitoring of correct operation, for instance. Diagnostic and fault finding or fault reporting signals may also be required. It is conventional in aircraft design to provide direct links between the source of any signal and its destination, often duplicated to provide redundancy for safety reasons. The provision of a direct link for each required signal route allows the format of signal to be optimised for that route, by choice of transmission technique, design and choice of technology for the transmission path, and the like. However, the result is a complex loom of wiring which incorporates many possible fault locations, adding significant mass to the aircraft and making fault finding difficult.
The present invention provides a signalling system for an aircraft which incorporates a plurality of items of plant, the system comprising a plurality of nodes arranged into a hierarchy of at least three levels, the nodes of each level above the lowest level being connected by signal transmission means to a plurality of nodes lower in the hierarchy.
Preferably each node at the lowest level is associated with an item of plant, for communication therewith. Nodes are preferably selected for connection to a higher level node by reference to their proximity to that higher level node. Preferably, at least those nodes above the lowest level include at least some decision-making capability, and are operable to transmit in response to a signal received from a lower level node. Each node with decision-making capability may be authorised to make decisions to a level set in accordance with the level of the node in the hierarchy, and to pass a signal to a higher node in the event that a decision above the authorised level is required. Each node is preferably operable to pass signals from a lower level node to which the node is connected, to another lower level node to which the node is connected, without requiring communication with a higher level node.
Preferably, signals passed between nodes include plant control signals, and/or signals indicating the status or performance of plant, and/or diagnostic signals, and/or signals indicating power requirements of plant.
Preferably at least one node is capable of responding to power requirement signals to produce control signals for power generators of the aircraft. Preferably at least one node is capable of recording diagnostic signals for subsequent analysis. Preferably at least one node is capable of responding to plant status or performance signals and to produce modified plant control signals in response thereto and to the required plant status and performance.
The signal transmission means may include a plurality of links between nodes and operating according to different transmission formats. The transmission formats may include electrical, and/or electromagnetic, and/or hydraulic, and/or pneumatic transmission formats. At least some nodes are preferably connected to links of different transmission formats and are provided with conversion means operable to provide conversion between formats.
Preferably at least one node is operable to control operation of a power delivery system of the aircraft. Items of plant are preferably grouped within the aircraft, the items of a group being provided with power by a distribution arrangement from a common point in the power delivery network of the aircraft, there being a node corresponding to the common point and connected with lower level nodes corresponding only with members of the group. Preferably the node corresponding with the common point is operable to control the operation of power distribution means which distribute power to the group members from the common point.
Preferably the signal transmission means includes at least one link which connects two nodes and provides a plurality of independent communication paths between the nodes.